Manufacture of alcohols



Patented Nov. 2, 1937 NETED ST ATENT OFFICE Young,

Los Angeles, Calif.,

and Frank S.

Crossley, Philadelphia, Pa., assignors to Sharp & Dohme, Incorporated, Philadelphia, Pa., a corporation of Maryland No Drawing. Application June 19, 1935, Serial No. 27,348

11 Claims.

This invention relates to the reduction of aldehydes to the corresponding alcohols and more particularly to the reduction of unsaturated aldehydes, such as crotch-aldehyde, cinnam-aldehyde, etc., to the corresponding unsaturated alcohols.

Various processes have been proposed for the reduction of aldehydes to alcohols, but only a limited number of methods have been proposed for the reduction of aldehydes having an unsaturated radical, for example a vinyl group or a substituted vinyl group, where it is not desired to reduce the unsaturated group; and the methods heretofore proposed have not, according to 13 our experience, proven satisfactory. It has been proposed for example to reduce croton-aldehyde by means of a zinc-copper couple; but we have found that this method gave only low yields and a product contaminated with butyl, that is hydrogenated or reduced, crotyl alcohol. It has also been proposed to reduce unsaturated aldehydes by means of aluminum ethoxide and chlor magnesium ethoxide; but such methods result in the oxidation of the ethoxy group to acetaldehyde; and we have found the yields obtained by such methods were small.

We have found that unsaturated aldehydes, for example, croton-aldehyde, can be reduced to the unsaturated alcohols, forexample crotyl al- 39 001101, and a product obtained satisfactory in both yield and purity, by carrying out the reduction with the use of secondary alkoxides of aluminum, particularly, aluminum isopropoxide.

Crotyl alcohol, a homolog of allyl alcohol, is a valuable product for use as an intermediate and for other purposes; and we have found that this alcohol can be readily prepared with satisfactory yield and of satisfactory purity by the present process. Other unsaturated alcohols, such as those hereafter referred to, can be similarly produced from the corresponding unsaturated aldehydes.

The reducing agents used in the present process are secondary metallic alkoxides, such as aluminum alkoxides having the general formula A1(OR)3, in which R is an alkyl radical, and in which the alkoxy group is a secondary alkoxy group which will be oxidized to a ketone rather than an aldehyde The simplest of such compounds is aluminum isopropoxide which is an effective reducing agent for the unsaturated aldehydes and which on oxidation gives acetone which is readily volatile. Instead of aluminum isopropoxide other secondary aluminum alkoxides can be used, for example, aluminum secondary butoxide which on oxidation gives the ethyl methyl ketone having a somewhat higher boil-- ing point than acetone. By using a secondary metallic alkoxide which on oxidation gives a volatile ketone, the formation of aldehydes by oxidation of the alkoxide is obviated. The process is distinguished from processes in which a metallic ethoxide is used which on oxidation gives acetaldehyde which enters the. field of reaction and complicates it.

The present process is well adapted for use for the production of high yields and large amounts of the unsaturated alcohols.

The invention is illustrated by the following specific examples but it will be understood that the invention is not limited thereto as other aldehydes may be reduced in a similar manner and other aluminum alkoxides may be used. In the following examples the parts given are by weight.

Example 1. mm alcohol from crown-aldehyde Into a glass distilling vessel equipped with a reflux condenser connected to a watercooled downward distilling condenser is placed a solution of 252 parts of pure crotch-aldehyde in 420 parts of benzene. To this is added 244.8 parts of aluminum isopropoxide (corresponding to a molecular ratioof crotch-aldehyde to aluminum isopropoxide of 3:1) in 280 parts of benzene. The distilling vessel is gently warmed by a steam jacket so that a slow distillation occurs, and the heating is continued until about 180 parts of distillate is collected over a period of e. g. 5 to 6 hours. This distillate is mainly acetone, although toward the end of the distillation it contains a considerable proportion of benzene. The rate of heating is now increased, so that most of the benzene comes off rapidly. The residue in the flask is acidified with an excess of 20% sulfuric acid, and extracted several times with benzene. The combined benzene extractions are Washed once with a little water, dried, and fractionated. The portion boiling at 115-125" C. is collected as crude crotyl alcohol, and on refractionation yields crotyl alcohol boiling at 121-l22.

Ecample 2.Cr0tyl alcohol from crown-aldehyde 47 parts of aluminum turnings or wire are placed in a still with 400 parts of commercial 98% isopropyl alcohol and 2.5 parts of mercuric chloride. The mixture is refluxed until all of the aluminum has reacted, after which 210 parts of crotch-aldehyde and 480-560 parts of isopropyl alcohol are added and the heating and refluxing is continued, with slow distillation of the acetone formed. The mixture is slowly distilled for e. g. 8-9 hours, the temperature of the vapors being kept, at 60-70 C. by maintaining the temperature of the heating jacket at about 110 C. The reflux column is then removed or disconnected, and the solvent is distilled off, using an eificient condensing device to recover the solvent, which may be used again. When the reaction mixture has cooled to 40 C. it is hydrolyzed with 900 parts of 6N sulfuric acid, and allowed to cool to room temperature. The acidified mass separates into two phases, an oil phase and an aqueous phase, which are separated. The oil phase is distilled at reduced pressure, the distilling temperature being maintained at 60- 70 C. by slowly lowering the pressure from 275 mm. to 65 mm. When the distillation slows down, the pressure is reduced to 20 mm. and the temperature allowed to rise to -100 C., insuring removal of the last of the crotyl alcohol without obtaining higher boiling polymerization products.

The aqueous phase is also distilled, the distillation being continued until it no longer gives a positive response to a test for the presence of unsaturated bodies. This usually occurs when the distillation temperature reaches 99-100 C. The distillate is treated with potassium carbonate, and combined with the crude alcohol distillate from the oil phase. The resulting mixture is dried with potassium carbonate, and distilled through a reflux column. The portion boiling between 117 C. and 122 C. is collected and refractionated.

' Example 3.C'itronellol from citronellal 40.8 parts of aluminum isopropoxide and about 270 parts of benzene are placed in a still equipped with an air cooled reflux condenser connected to a downward directing condenser. The mixture is heated to the boiling point by means of a steam jacket, and, when solution is nearly complete, 92.4 parts of citronellal (3 mols to 1 mole of the isopropoxide) are added. Heating is continued, and after a short time the mixture assumes a yellow color. The rate of heating is so regulated that a slow distillation is maintained, about 200 parts of distillate being collected over e. g. 3 -4 hours. The mixture is then allowed to cool, and is mixed with an excess of 20% sulfuric acid, that is, sufiicient acid to dissolve the gelatinous precipitate which first forms. The upper organic layer is drawn ofi, washed twice with a solution of sodium carbonate, and distilled. The fraction boiling at 222-224 C. at atmospheric pressure is collected as citronellol.

Example 4.C'mnamyl alcohol from cinnamic aldehyde Example 5.Butyl alcohol from butyraldehyde 259 parts of freshly distilled butyraldehyde and 400 parts of benzene are placed in a still similar to that described in Example '3. To this is added a solution of 244.8 parts of aluminum isopropoxide (1 mole to 3 mols of the butyraldehyde) in 240 parts of benzene. The reaction is regulated as in Example 3, and the product isolated in a similar manner. Butyl alcohol, B. P. 116-118 C. and butyl butyrate, B. P. 163-166 C. are obtained.

Example 6.C'rotyl alcohol from crown-aldehyde The 244.8 parts of aluminum isopropoxide of Example 1 are replaced by 295.2 parts of aluminum secondary butoxide,

OH: A1 O H and the reaction carried out as in Example 1, except that the methyl ethyl ketone formed, is distilled over at a somewhat higher temperature.

Other aluminum secondary alkoxides, prepared from aluminum and a secondary alcohol, may be used in a similar manner, and other solvents may be used. Also other aldehydes, both saturated and unsaturated, can be similarly reduced to the corresponding alcohols.

We claim:

1. The process of reducing aldehydes to the corresponding alcohols which comprises subjecting said aldehydes to the action of a secondary alkoxide of aluminum.

2. The process of reducing aldehydes to the corresponding alcohols which comprises subjecting said aldehydes to the action of aluminum isopropoxide.

3. The process of'reducing unsaturated aldehydes to the corresponding unsaturated alcohols which comprises subjecting said unsaturated aldehydes to the action of a secondary alkoxide of aluminum.

4. The process of reducing unsaturated aldehydes to the corresponding unsaturated alcohols which comprises subjecting said unsaturated aldehydes to the action of aluminum isopropoxide.

5. The process of reducing croton-aldehyde to the crotyl alcohol which comprises subjecting said croton-aldehyde to the action of a secondary aluminum alkoxide.

6. The process of reducing croton-aldehyde to the crotyl alcohol which comprises subjecting said croton-aldehyde to the action of aluminum isopropoxide.

'7. The process of reducing cinnamic aldehyde to the cinnamyl alcohol which comprises subjecting said cinnamic aldehyde to the action of a secondary aluminum alkoxide.

8. The process of reducing cinnamic aldehyde to the cinnamyl alcohol which comprises subjecting said cinnamic aldehyde to the action of aluminum isopropoxide.

9. The process of reducing citronellal to citronellol which comprises subjecting said citronellol to the action of a secondary aluminum alkoxide.

10. The process of reducing citronellal to citronellol which comprises subjecting said citronellol tothe action of aluminum isopropoxide.

11. The process of reducing aldehydes to corresponding alcohols which comprises subjecting such aldehydes to the action of an aluminum alkoxide which on oxidation yields a readily volatile alkyl ketone.

WALTER H. HARTUNG. WILLIAM G. YOUNG. FRANK S. CROSSLEY.

, C RTIFICATE O CORRECTION. Patent No. 2,098,206\

of the above numbered patent z 'equiring correction as follower Page 2 second column, line 17, in the formula, for "0 0 read C H and that the said Letters Patent should be read with this correction therein that-the same may cohionn to the recorj'd of the case in the Patent Office.

sig ed and sealed this 25th day of Januar A. -D. 1958.

Henry Van'Arsdele'; (Seal) Acting Cemmis'sioner of Patents; 

